The structure of organic electroluminescent devices (OLEDs) in which organic semiconductors are employed as functional materials is described, for example, in U.S. Pat. Nos. 4,539,507, 5,151,629, EP 0676461 and WO 98/27136. The emitting materials employed here are increasingly organo-metallic complexes which exhibit phosphorescence instead of fluorescence (M. A. Baldo et al., Appl. Phys. Lett. 1999, 75, 4-6).
In accordance with the prior art, the hole-transport materials used in the hole-transport layer or in the hole-injection layer are, in particular, triaryl-amine derivatives which frequently contain at least two triarylamino groups or at least one triarylamino group and at least one carbazole group. These compounds are frequently derived from diarylamino-substituted triphenyl-amines (TPA type), from diarylamino-substituted biphenyl derivatives (TAD type) or combinations of these base compounds. Use is also frequently made of spirobifluorene derivatives which are for example substituted by diarylamino groups (for example in accordance with EP 676461 or U.S. Pat. No. 7,714,145). There is still a demand here for alternative materials that can be used in OLEDs devices in order to obtain devices with good properties in terms of efficiency, lifetime and operating voltage.
Therefore, the object of the present invention is to provide compounds which are suitable for use in a fluorescent or phosphorescent OLED, in particular a phosphorescent OLED, for example as hole-transport material in a hole-transport or exciton-blocking layer or as matrix material in an emitting layer.